Optical Characterization of AlAsSb Digital Alloy and Random Alloy on GaSb

Juang, Bor Chau; Liang, Baolai; Ren, Dingkun; Prout, David; Chatziioannou, Arion F.; Huffaker, Diana L.

doi:10.3390/cryst7100313

Cited by 8 publications

(7 citation statements)

References 28 publications

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“…The GaSb/AlAsSb SAM‐APD structure shown in Figure was grown on an n‐type GaSb (001) substrate by a Veeco Gen930 solid‐source molecular‐beam epitaxy (MBE) reactor. The AlAsSb films were realized via digital alloy growth technology by periodically alternating the arsenic (As) and antimony (Sb) shutters while maintaining a steady aluminum (Al) flux, resulting in an equivalent AlSb/AlAs sequence of 4.0/0.44 monolayers . Figure a shows a high‐resolution cross‐sectional transmission electron microscopy (TEM) image of the AlAsSb digital alloy layer and its diffraction pattern.…”

Section: Experiments Results and Discussionmentioning

confidence: 99%

Energy‐Sensitive GaSb/AlAsSb Separate Absorption and Multiplication Avalanche Photodiodes for X‐Ray and Gamma‐Ray Detection

Juang

Chen

Ren

et al. 2019

Advanced Optical Materials

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and multiplication avalanche photodiodes (SAM-APDs) composed of photoabsorbers and large bandgap multiplication regions are advantageous for achieving highefficient and low-noise photodetection with high-energy resolution. [11][12][13] Such a detector architecture can be also applied to energy-sensitive gamma-ray and X-ray detection. A GaAs/AlGaAs SAM-APD comprised of a 4.5 µm absorption region and a staircase-like multiplication region has been developed for X-ray photodetection. [14] Meanwhile, a similar GaAs/ Al 0.8 Ga 0.2 As SAM-APD structure has been also demonstrated to detect soft X-rays at 5.9 keV with a full-width half-maximum (FWHM) of 1.08 keV. [15] However, its spectroscopic characterizations show an undesired secondary peak located at energy lower than the 5.9 keV peak. This is because of 1) different degrees of impact ionization experienced by the electrons and holes; [16][17][18] 2) insufficient layer thickness ratio; [19] and 3) inadequate difference of pair creation energy (PCE) between GaAs and AlGaAs. [20,21] Indeed, the absorption efficiency can be improved by simply increasing the thickness of the absorption layer. Unfortunately, the commonly used (Al)GaAs semiconductors are not able to concurrently offer high-Z (i.e., high atomic number) absorption and large PCE difference within SAM structures for highenergy X-ray or gamma-ray detection.Alternatively, the antimony-based (Sb-based) SAM-APD structure with high-Z GaSb and large bandgap AlAsSb is promising. GaSb absorbers can provide a much higher probability than GaAs to stop X-ray and gamma-ray photons at a given energy due to a relatively higher Z. [22] In addition, the GaSb/AlAsSb material system provides a larger dissimilarity in both PCE and absorption efficiency. [23,24] This allows for a significant suppression of spurious photopeaks, which are generated outside the intended absorption regions. The combination of these unique capabilities shows promise for achieving X-ray and gamma-ray detectors with high spectroscopic performance. To prove the concept, we develop GaSb/AlAsSb SAM-APDs composed of 2 µm GaSb absorbers and AlAsSb digital alloy multiplication regions to detect X-ray and gamma-ray photopeaks under irradiation from 241 Am sources. Due to the reduced high-peak electric Demonstrated are antimony-based (Sb-based) separate absorption and multiplication avalanche photodiodes (SAM-APDs) for X-ray and gamma-ray detection, which are composed of GaSb absorbers and large bandgap AlAsSb multiplication regions in order to enhance the probability of stopping highenergy photons while drastically suppressing the minority carrier diffusion. Well-defined X-ray and gamma-ray photopeaks are observed under exposure to 241 Am radioactive sources, demonstrating the desirable energy-sensitive detector performance. Spectroscopic characterizations show a significant improvement of measured energy resolution due to reduced high-peak electric field in the absorbers and suppressed nonradiative recombination on surfaces. Additionally, the GaSb/AlAsSb SAM...

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Section: Experiments Results and Discussionmentioning

confidence: 99%

Energy‐Sensitive GaSb/AlAsSb Separate Absorption and Multiplication Avalanche Photodiodes for X‐Ray and Gamma‐Ray Detection

Juang

Chen

Ren

et al. 2019

Advanced Optical Materials

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“…The AlAsSb p-i-n and n-i-p structures used in this study were grown on epi-ready n-InP (001) and p-InP (001) substrates respectively, via a digital alloy growth technology in a Veeco GEN930 MBE reactor, in which both As2 and Sb2 fluxes are supplied using valved cracker cells [20]. The challenge here was to grow a thick ternary random alloy with two group V elements (As and Sb).…”

Section: Device Growth and Fabricationmentioning

confidence: 99%

Extremely low-noise avalanche photodiodes based on AlAs0.56Sb0.44

Xie

Liang

et al. 2020

Emerging Imaging and Sensing Technologies for Security and Defence V; And Advanced Manufacturing Technologies for Micro- And Na

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This paper presents the electron and hole avalanche multiplication and excess noise characteristics based on bulk AlAs0.56Sb0.44 p-in and n-i-p homojunction diodes lattice matched to InP, with nominal avalanche region thicknesses of 0.6-1.5 µm. From these, the bulk electron and hole impact ionization coefficients (α and β respectively), have been determined over an electric field range of 220-1250 kV/cm for α and from 360-1250 kV/cm for β for the first time. Excess noise characteristics suggest an β/α ratio as low as 0.005 for an avalanche region of 1.5 µm in this material, close to the theoretical minimum and significantly lower than AlInAs, InP, or even silicon. This material can be easily integrated with InGaAs for networking and sensing applications, with modeling suggesting that a sensitivity of-32.1 dBm at a bit-error rate (BER) of 1×10-12 at 10 Gb/s at 1550 nm can be realized. This sensitivity can be improved even further by optimizing the dark currents and by using a lower noise transimpedance amplifier.

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“…The GaSb nanostructures are widely applied in thermo-photovoltaic cells, solar cells and photodetectors due to their high carrier mobility and bandgap engineering flexibility. [1][2][3][4][5][6] However, the unpassivated GaSb devices are prone to high trap state density from unterminated dangling bonds and native oxides. These native oxides are formed via the following reactions: [7] 2…”

Section: Introductionmentioning

confidence: 99%

Optimization of surface passivation for suppressing leakage current in GaSb PIN devices

Azizur-Rahman

Chang

et al. 2020

Electron. lett.

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The suppression of leakage current via surface passivation plays a critical role for GaSb‐based optoelectronic devices. In this Letter the authors carefully optimise the sulfur passivation parameters for improving the performance of GaSb p–i–n devices. Two competing processes are evaluated during the sulfur passivation process: the hydrolysis of HS– ions that aide surface passivation and the re‐oxidation, respectively. Upon the optimisation of sulfur passivation parameters and subsequent encapsulation with atomic layer deposition Al2 O3, the surface resistivity significantly increased from 4.3 kΩ.cm to 28.6 kΩ.cm, leading to a 19.1 times drop in dark current at room temperature for the GaSb p–i–n structure. This Letter provides a repeatable and stable passivation approach for improving the optoelectronic performance of GaSb‐based devices.

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Optical Characterization of AlAsSb Digital Alloy and Random Alloy on GaSb

Cited by 8 publications

References 28 publications

Energy‐Sensitive GaSb/AlAsSb Separate Absorption and Multiplication Avalanche Photodiodes for X‐Ray and Gamma‐Ray Detection

Energy‐Sensitive GaSb/AlAsSb Separate Absorption and Multiplication Avalanche Photodiodes for X‐Ray and Gamma‐Ray Detection

Extremely low-noise avalanche photodiodes based on AlAs0.56Sb0.44

Optimization of surface passivation for suppressing leakage current in GaSb PIN devices

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